Mixing assembly for mixing bone cement

ABSTRACT

A mixing assembly for mixing bone cement includes a housing, a lid, a handle, and two mixing paddles, a first and a second mixing paddle. The lid is removably attachable to the housing. The handle has a portion that extends through the lid and that is rotatable in a first rotational direction. The first mixing paddle is operatively coupled to the portion of the handle. As a result, the first mixing paddle rotates with the portion of the handle in the first rotational direction. The second mixing paddle is operatively coupled to the first mixing paddle for rotating opposite the portion. As such, when the portion of the handle and the first mixing paddle rotate in the first rotational direction, the second mixing paddle rotates in a second rotational direction that is opposite the first rotational direction.

RELATED APPLICATIONS

This patent application claims priority to and all advantages of U.S.Provisional Patent Application No. 60/364,171, which was filed on Mar.14, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention generally relates to a mixing assembly for mixingbone cement.

2. Description of the Related Art

The application of bone cement to a bone during surgical procedures,such as the attachment of a prosthesis or pathological fracturefixation, is well known in the surgical community. With regard to theattachment of a prosthesis, the cement is packed into the bone and theprosthesis is then attached. The cement cures and a bond developsbetween the bone and the prosthesis. Other uses of bone cement includerepairing or mending bone fractures or shattered bone occurring fromextreme trauma. Bone cement may also be used during cosmetic or dentalsurgery. Moreover, bone cement may be used as a drug delivery or releasesystem, whereby the bone cement is mixed with antibiotics or otherdesired drugs and applied to a specific surgical site such that thedrugs leach out and are delivered directly to the surgical site. Somebone cements are also designed to be absorbed by the body over time.

Typically, the bone cement is prepared by thoroughly blending twocomponents. Typical bone cement mixtures comprise a powdered polymer orcopolymer, such as a polymethylmethacrylate, and a liquid monomer,usually a methylmethacrylate. Conventionally, the combining of thepowder and liquid components is carried out using a container and aspatula resulting in the formation of a quick setting bone cementmaterial. Because of its quick setting nature, the bone cement isusually prepared in the surgical room in conjunction with the surgicalprocedure. Once the bone cement is thoroughly mixed, the surgeonpromptly removes the necessary amount of cement, inserts it into adelivery device or manipulates it by hand, and applies it to theappropriate surface or cavity before the cement mixture cures orhardens. However, there are a number of disadvantages to this method ofmixing bone cement.

First, combining the monomer liquid and polymer powder causes noxiousfumes to be emitted. Thus, it is desirable to prevent these fumes fromescaping into the atmosphere. Second, the cement ingredients must bemixed quickly, thoroughly and uniformly to maximize homogeneity whilereducing or eliminating the formation of air bubbles to impart highmechanical strength and bonding properties to the bone cement. Inherentin the mixing process, air bubbles are generated in the mixture from airresiding in the powder and in the mixing container. Moreover, airbubbles are produced when the monomer vaporizes to produce a gas duringthe mixing process.

To evacuate the maximum amount of air and gas entrapped in the containerand mixture, it is known in the art to perform the mixing in a mixingchamber under vacuum. Further, various devices are available whereincement may be mixed under vacuum. Such devices include a mixing chambercoupled with a dispensing syringe connected to a vacuum source. Althoughsuch devices are efficient and clean, they are expensive and inhibitapplication of the cement compound by hand, which may be the preferredor necessary method in a given procedure.

Alternatively, mixing assemblies, i.e., cement mixing bowls, are alsoknown in the art. Such mixing bowls generally include a housing and alid defining a mixing chamber with a mixing paddle extending into thehousing and disposed in the mixing chamber. Typically, the mixing paddleis rotated, i.e., driven by a handle extending out of the lid. Inaddition, the mixing chamber is generally connectable to a vacuum sourcefor creating a vacuum within the mixing chamber.

Such mixing bowls are disclosed in U.S. Pat. Nos. 5,494,349 and6,254,268. These mixing bowls are deficient for a variety of reasons.Overall, these mixing bowls do not provide adequate mixing and do notpermit establishment of a sufficient hermetic seal. For example, themixing bowl disclosed in the '349 patent to Seddon does not provideadequate mixing of the monomer liquid and polymer powder. Morespecifically, the single mixing paddle disclosed in the '349 patent,which only rotates in one direction, does not adequately mix the monomerliquid and the polymer powder. Ultimately, inadequate mixing of thesetwo components results in a bone cement that lacks the requiredmechanical strength and bonding properties. The mixing bowl disclosed inthe '349 patent is also deficient because the mixing paddle is notadequately biased against an interior wall of the housing, specificallya bottom interior wall, to sufficiently scrape the bone cement from theinterior wall. As a result, excessive air and gas bubbles can remainpresent in the bone cement, which is detrimental to various propertiesof the cement. Instead, to have this mixing paddle adequately biasedagainst the interior wall of the housing, the lid either cannot betightened about the housing such that a completely hermetic seal is notestablished, or the lid has to be tightened too much about the housingsuch that the completeness of any hermetic seal is sacrificed. Morespecifically, the lid in the '349 is particularly susceptible todeflection when the mixing bowl is under vacuum. This deflection may‘pinch’ the mixing paddle at the bottom interior wall such thatincreased torque is required to mix the bone cement. When the mixingbowl of the '349 patent is not under vacuum, there is typically a largegap between the mixing paddle and the interior wall of the housing. Themixing bowl of the '349 patent is further deficient in that it does notstrategically incorporate a gear set that provides for more than onemixing paddle and for more than one rotational direction for optimummixing of the bone cement. The mixing bowl disclosed in the '268 patentto Long realizes theses same deficiencies.

Due to the deficiencies associated with the mixing assemblies of theprior art, including those described above, it is desirable to provide aunique mixing assembly that solves one or more of these deficiencies.

SUMMARY OF THE INVENTION AND ADVANTAGES

A mixing assembly for mixing bone cement is disclosed. The mixingassembly includes a housing having an interior wall and a lid that isremovably attachable to the housing. The mixing assembly also includes ahandle and a first and second mixing paddle. The handle includes aportion that extends through the lid and that is rotatable in a firstrotation direction. The first mixing paddle is operatively coupled tothe portion of the handle for rotating with the portion of the handle inthe first rotational direction. The second mixing paddle is operativelycoupled to the first mixing paddle for rotating opposite the portion ofthe handle. As such, when the portion and the first mixing paddle rotatein the first rotational direction, the second mixing paddle rotates in asecond rotational direction that is opposite the first rotationaldirection.

In a further embodiment of the subject invention, the lid of the mixingassembly, which is removably attachable to the housing, is movablebetween an open position and a sealed position. In the open position,the bone cement can be added to the housing, and in the sealed position,the lid is hermetically sealed to the housing to define a sealed mixingchamber between the lid and the interior wall of the housing for mixingthe bone cement. This particular embodiment may only include one mixingpaddle, specifically the first mixing paddle, is operatively coupled tothe portion of the handle for rotating with the portion. The mixingpaddle is movable between an extended position when the lid is in theopen position and a retracted position. When the lid is in the sealedposition and the mixing paddle is in the retracted position, the mixingpaddle is adapted to scrape the bone cement from the interior wall whenthe lid is in the sealed position. A resilient member is disposedbetween the portion of the handle and the mixing paddle. The resilientmember normally-biases the mixing paddle into the extended position.However, the resilient member also compresses in response to contactbetween the mixing paddle and the interior wall as the lid is moved fromthe open position to the sealed position. This compression permits themixing paddle to retract into the retracted position such that the lidcan be hermetically sealed to the housing in the sealed position. Inthis position, the mixing paddle can still scrape the bone cement fromthe interior wall.

In yet a further embodiment of the subject invention, the mixingassembly incorporates a gear set that is disposed between the first andsecond mixing paddles. The gear set operatively couples the secondmixing paddle to the first mixing paddle such that the second mixingpaddle rotates opposite the portion of the handle in the secondrotational direction and about a second fixed axis or rotation when theportion and the first mixing paddle are rotating in the first rotationaldirection about a first fixed axis of rotation.

The primary advantage of the present invention is that the mixingassembly provides adequate mixing of a monomer liquid and polymerpowder, which results in a bone cement that has sufficient mechanicalstrength and bonding properties. The first and second mixing paddles,and more specifically the opposite rotational directions respectivelyassociated with the first and second mixing paddles, enable the adequatemixing. With adequate mixing, the bone cement is conducive to manydifferent application techniques including application of the bonecement by hand. The mixing assembly of the subject invention alsoenables a complete hermetic seal to be established between the housingand the lid such that fumes and the monomer and polymer components donot escape from the sealed mixing chamber.

Further, the mixing paddle utilized in the mixing assembly of thesubject invention is biased against the interior wall of the housing, bythe resilient member, such that the mixing paddle can sufficientlyscrape the bone cement from the interior wall. This further enhancesmixing and eliminates excessive air and gas bubbles from the bonecement. Furthermore, by scraping the bone cement, the mixing paddlereduces the amount of any unmixed powder such that a more complete,homogeneous mix of the bone cement can be attained. Also, a complete,and lasting, hermetic seal is established with this mixing bowl as thelid is moved about the housing, even while the mixing paddle is biasedagainst the interior wall of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a view of a mixing assembly according to one embodiment of thepresent invention;

FIG. 2 is a partially cross-sectional view of the mixing assembly ofFIG. 1;

FIG. 3 is another partially cross-sectional view of the mixing assemblyof FIG. 1;

FIG. 4 is a perspective view illustrating, in particular, a lid, ahandle, first and second mixing paddles, and a gear set according to themixing assembly of FIG. 1;

FIG. 5 is a perspective of view of a housing of the mixing assembly ofthe present invention;

FIG. 6 is a top view of the lid illustrating the handle and a vacuumport defined within the lid;

FIG. 7 is a partially cross-sectional view of the mixing assemblyaccording another embodiment of the present invention;

FIG. 8 is another partially cross-sectional view of the mixing assemblyof FIG. 7;

FIG. 9 is a partially cross-sectional view of the mixing assemblyaccording to another embodiment of the present invention;

FIG. 10 is a partially cross-sectional view of the mixing assemblyaccording to another embodiment of the present invention;

FIG. 11 is a cross-sectional view illustrating the housing;

FIG. 12 is a perspective view of the mixing assembly according toanother embodiment of the present invention;

FIG. 13 is a partially cross-sectional view of the mixing assemblyaccording to another embodiment of the present invention thatillustrates, in particular, an alternative disposition for the handle;

FIG. 14 is a partially cross-sectional view of the mixing assemblyaccording to another embodiment of the present invention;

FIG. 15 is a cross-sectional view of the lid of the mixing assembly ofFIG. 14;

FIG. 16 is a top plan view of the housing of the mixing assembly of FIG.14;

FIG. 17 is an enlarged view of a locking ramp of the mixing assembly ofFIG. 14;

FIG. 18 is a cross-sectional view of the handle of the mixing assemblyof FIG. 14;

FIG. 19 is a perspective view of the handle of the mixing assembly ofFIG. 14;

FIG. 20 is a cross-sectional view of a knob of the mixing assembly ofFIG. 14;

FIG. 21 is a partially cross-sectional view of the mixing assemblyaccording to another embodiment of the present invention;

FIG. 22 is a partially cutaway perspective view of the mixing assemblyaccording to another embodiment of the present invention;

FIG. 23 is a cross-sectional view of the mixing assembly of FIG. 22;

FIG. 24 is partially cross-sectional view of the mixing assembly of FIG.22;

FIG. 25 is another cross-sectional view of the mixing assembly of FIG.22;

FIG. 26 is a view of the mixing assembly illustrating a portion of thehandle and the handle;

FIG. 27 is a cross-sectional view of a first end of the first mixingpaddle for the mixing assembly of FIG. 22;

FIG. 28 is a perspective view of one embodiment of the second mixingpaddle for use in the mixing assembly of the subject invention;

FIG. 29 is a perspective view of another embodiment of the second mixingpaddle for use in the mixing assembly of the subject invention;

FIG. 30 is a perspective view of another embodiment of the second mixingpaddle for use in the mixing assembly of the subject invention;

FIG. 31 is a perspective view of one embodiment of the first mixingpaddle for use in the mixing assembly of the subject invention;

FIG. 32 is a perspective view of another embodiment of the second mixingpaddle for use in the mixing assembly of the subject invention;

FIG. 33 is a perspective view of another embodiment of the first mixingpaddle for use in the mixing assembly of the subject invention;

FIG. 34 is a perspective view of another embodiment of the second mixingpaddle for use in the mixing assembly of the subject invention;

FIG. 35 is a perspective view of another embodiment of the second mixingpaddle for use in the mixing assembly of the subject invention;

FIG. 36 is a perspective view of other embodiment of the first andsecond mixing paddles for use in the mixing assembly of the subjectinvention;

FIG. 37 is a partially cutaway perspective view of the mixing assemblyaccording to another embodiment of the present invention thatillustrates the portion of the handle and the first mixing paddlerotating in a first rotational direction and the second mixing paddlerotating in a second rotational direction;

FIG. 38 is a partially cutaway perspective view of the mixing assemblyaccording to another embodiment of the present invention thatillustrates the portion of the handle and the first mixing paddle beingrotatable is a first rotational direction and in a second rotationaldirection, and the second mixing paddle being rotatable in the first andsecond rotational direction so long as the second mixing paddle rotatesopposite the portion and the first mixing paddle;

FIG. 39 is a partially cutaway perspective view of the mixing assemblyaccording to another embodiment of the present invention thatillustrates the portion of the handle, the first mixing paddle, and thesecond mixing paddle rotating in a first rotational direction;

FIG. 40 is a cross-sectional view of the mixing assembly illustratingthe lid in an open position with no gap between a first set of tabs andan annular flange of the first mixing paddle;

FIG. 41 is a cross-sectional view of the mixing assembly disclosed inFIG. 40 illustrating the lid in a sealed position with a gap between thefirst set of tabs and the annular flange of the first mixing paddle;

FIG. 42 is a cross-sectional view of the mixing assembly according toanother embodiment of the present invention illustrating a third mixingpaddle; and

FIG. 43 is a partially cross-sectional side view of the mixing assemblyillustrating tabs on the lid and ramps on a rim of the housing forlocking the lid to the housing in the sealed position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring primarily to FIGS. 22 through 43, wherein like numeralsindicate like or corresponding parts throughout the several views, amixing assembly for mixing bone cement is generally shown at 10. Forease of description, the mixing assembly 10 may also be referred toherein as a bone cement mixing bowl assembly. The mixing assembly 10includes a housing 12 and a lid 14. The housing 12 is further defined asa bowl. Consequently, the housing 12 may be referred to herein as a bowlor a mixing bowl. The housing 12 includes at least one interior wall 16and a base 18 for providing addition support and stability to thehousing 12. As disclosed in FIGS. 23 and 24, the mixing assembly 10 alsopreferably includes a depression 20 that is defined within the housing12. The significance of this depression 20 is described below.

The lid 14 is removably attached to the housing 12, and a sealed mixingchamber 22 is defined between the lid 14 and the interior wall 16 of thehousing 12. Of course, this sealed mixing chamber 22 exists once the lid14 is attached to the housing 12. The bone cement is mixed in the sealedmixing chamber 22. Preferably, a vacuum port 24 is defined within thelid 14. The vacuum port 24 is particularly adapted for attaching asource to create a vacuum within the mixing assembly 10, as desired. Thevacuum removes fumes from the mixing assembly 10 and, more importantly,the vacuum pulls air/porosity out of the bone cement. Because the lid 14is removably attachable to the housing 12, the lid 14 can be removedfrom the housing 12 to insert the bone cement and the lid 14 can beattached to the housing 12 as described additionally below.

The mixing assembly 10 also includes a handle 26. The handle 26 has aportion 28 that extends through the lid 14. The handle 26 is rotatableabout the lid 14. More specifically, the handle 26 is rotatable in afirst rotational direction. More specifically, a first sleeve 30 isdefined within and extends entirely through the lid 14 for supportingthe portion 28 of the handle 26. The portion 28 of the handle 26 extendsthrough the first sleeve 30 to extend through the lid 14 and at leastpartially into the sealed mixing chamber 22. Furthermore, a secondsleeve 32, that is at least partially spaced from the first sleeve 30,extends from the lid 14. The significance of this second sleeve 32 isdescribed below.

The mixing assembly 10 of the subject invention also includes a firstmixing paddle 34 and a second mixing paddle 36. These paddles 34, 36 arealso referred to in the art as mixing blades. Preferably, the firstmixing paddle 34 includes a plurality of vanes 38 for mixing the bonecement. It is most preferred that these vanes 38 are concave and thatthe plurality of vanes 38 includes a first vane 38A and a second vane38B. This first vane 38A contacts the interior wall 16 for scraping thebone cement, and the second vane 38B is spaced from the interior wall 16for spreading, i.e., smearing, the bone cement.

The scraping of the bone cement from the interior wall 16 of the housing12 ensures that the bone cement is moved around within the sealed mixingchamber 22 such that sufficient mixing of the bone cement can occur, andthe spreading of the bone cement by the second vane 38B breaks a topsurface of the bone cement thereby releasing air and gas bubbles fromthe bone cement. In summary, the first vane 38A scrapes a consistentthickness of bone cement, and the second vane 38B smears this consistentthickness which ultimately results in more efficient removal of porosityfrom the bone cement. As disclosed in the Figures, the first mixingpaddle 34 rotates beneath and around the second mixing paddle 36. Morespecifically, the vanes 38 of the first mixing paddle 34 rotate beneathand around the second mixing paddle 36. Various structures for both thefirst and second mixing paddles 34, 36 are disclosed in FIGS. 28–36.These various structures for the first and second mixing paddles 34, 36are all significant because the first and second mixing paddles 34, 36are interchangeable as desired.

Regardless of the particular structure for the first mixing paddle 34,the first mixing paddle 34 includes a first end 40 and a second end 42.The first end 40 of the first mixing paddle 34 is adjacent the lid 14and is operatively coupled to the portion 28 of the handle 26. Morespecifically, the first end 40 of the first mixing paddle 34 isoperatively coupled to the portion 28 of the handle 26 that extendsthrough the first sleeve 30. As such, the first mixing paddle 34 rotateswith rotation of the handle 26, preferably in a 1:1 ratio with theportion 28 of the handle 26. The second end 42 of the first mixingpaddle 34, which is adjacent the housing 12 opposite the first end 40 ofthe first mixing paddle 34, is disposed in the depression 20.

Similarly, regardless of the particular structure for the second mixingpaddle 36, the second mixing paddle 36 also includes a first end 44 anda second end 46. The first end 44 of the second mixing paddle 36 isadjacent the lid 14 and is disposed within the second sleeve 32. Assuch, the second sleeve 32 extends from the lid 14 for supporting thesecond mixing paddle 36, specifically the first end 44 of the secondmixing paddle 36. The second end 46 of the second mixing paddle 36 isadjacent the housing 12 opposite the first end 44 of the second mixingpaddle 36.

Preferably, an annular flange 48 is disposed about the first mixingpaddle 34 at the first end 40, and at least one hole 50 is definedwithin the annular flange 48. The portion 28 of the handle 26 extendsinto the hole 50 to operatively couple the first mixing paddle 34 to theportion 28 of the handle 26. More specifically, as disclosed in FIG. 25,a first hole 50A and a second hole 50B are defined within the annularflange 48 of the first mixing paddle 34. The first hole 50A is defined180° apart from the second hole 50B. In this embodiment, the portion 28of the handle 26 includes a first set of tabs 52 (see FIG. 26) extendingaway from the handle 26. One of the tabs 52A extends into the first hole50A to engage the annular flange 48 at the first hole 50A. The other ofthe tabs 52B extends into the second hole 50B to engage the annularflange 48 at the second hole 50B. The mechanical interaction between thefirst and second holes 50A, 50B and the tabs 52A, 52B operativelycouples the first mixing paddle 34 to the portion 28 of the handle 26.

The first end 40 of the first mixing paddle 34 includes a post 54 thatextends from the annular flange 48. The portion 28 of the handle 26includes a socket 56. This socket 56 extends away from the handle 26 toreceive the post 54 of the first mixing paddle 34. This mechanicalinteraction between the post 54 of the first mixing paddle 34 and thesocket 56 of the handle 26 also operatively couples the first mixingpaddle 34 to the portion 28 of the handle 26. Although not required, itis preferred that the post 54 and the socket 56 are rectangular.

The mixing assembly 10 also includes a centering post 58. This centeringpost 58 is disposed within the socket 56 of the portion 28 of the handle26. A first resilient member 60 is disposed about the centering post 54,within the socket 56, and between the portion 28 of the handle 26 andthe first end 40 of the first mixing paddle 34. The first resilientmember 60 biases the first mixing paddle 34 which is describedadditionally below. Similarly, a second resilient member 62 is disposedwithin the second sleeve 32 between the lid 14 and the first end 44 ofthe second mixing paddle 36. The second resilient member 62 biases thesecond mixing paddle 36. As is understood by those skilled in the art,the first and second resilient members 60, 62 are also referred to inthe art as biasing devices.

The first mixing paddle 34 is operatively coupled to the portion 28 ofthe handle 26 for rotating with the portion 28 in the first rotationaldirection to mix the bone cement. The second mixing paddle 36 isoperatively coupled to the first mixing paddle 34 for rotating oppositethe portion 28 of the handle 26. As such, when the portion 28 and thefirst mixing paddle 34 rotate in the first rotational direction to mixthe bone cement, the second mixing paddle 36 rotates in a secondrotational direction that is opposite the first rotational directionalso to mix the bone cement. As a result, it is only required that thehandle 26 and its portion 28, and therefore the first mixing paddle 34,rotate in one rotational direction. This is represented in FIG. 37. Ofcourse, if the handle 26, its portion 28, and the first mixing paddle 34only rotate in one rotational direction, then a mechanical stop of someequivalent will be required to interact with, or otherwise engage, thehandle 26, its portion 28, and/or the first mixing paddle 34. Suchmechanical stops, which are known to those skilled in the art, wouldprevent rotation in a second rotational direction.

Although the portion 28 of the handle 26 and the first mixing paddle 34need only be rotatable in one rotational direction, and the secondmixing paddle 36 need only be rotatable in an opposite rotationaldirection, it is preferred that the portion 28 of the handle 26 and thefirst mixing paddle 34 are also rotatable in the second rotationaldirection that is opposite the first rotational direction. In thispreferred embodiment, the second mixing paddle 36 is also operativelycoupled to the first mixing paddle 34 such that the second mixing paddle36 rotates in the first rotational direction when the portion 28 and thefirst mixing paddle 34 are rotating in the second rotational direction.This is represented in FIG. 38.

Furthermore, although not required, it is preferred that the firstmixing paddle 34 is rotatable about a first fixed axis of rotation A1and the second mixing paddle 36 is rotatable about a second fixed axisof rotation A2 that is different from the first fixed axis of rotationA1. In this preferred embodiment, the first and second fixed axes ofrotation A1, A2 remain fixed throughout rotation of the first and secondmixing paddles 34, 36. The depression 20 defined within the housing 12,which was originally described above, is aligned with the first fixedaxis of rotation A1 to maintain the first fixed axis of rotation A1 andto stabilize the first mixing paddle 34 during rotation of the firstmixing paddle 34.

A gear set 64 is disposed between the first mixing paddle 34 and thesecond mixing paddle 36. This gear set 64 operatively couples the secondmixing paddle 36 to the first mixing paddle 34 such that the secondmixing paddle 36 rotates opposite the portion 28 in the secondrotational direction when the portion 28 and the first mixing paddle 34rotate in the first rotational direction. Similarly, in the embodimentwhere the portion 28 and the first mixing paddle 34 are also rotatablein the second rotational direction, the gear set 64 operatively couplesthe second mixing paddle 36 to the first mixing paddle 34 such that thesecond mixing paddle 36 rotates opposite the portion 28 in the firstrotational direction when the portion 28 and the first mixing paddle 34rotate in the second rotational direction.

Preferably, the gear set 64 includes a first gear 66 associated with thefirst mixing paddle 34 and a second gear 68 associated with the secondmixing paddle 36. More specifically, the first gear 66 is supported onthe annular flange 48 of the first mixing paddle 34 and the second gear68 is disposed at the first end 44 of the second mixing paddle 36. Thesecond gear 68 is recessed into the second sleeve 32. Once the secondmixing paddle 36 is assembled into the mixing assembly 10, and thesecond gear 68 is therefore recessed into the second sleeve 32, thefirst mixing paddle 34 is assembled into the mixing assembly 10 and theannular flange 48 of the first mixing paddle 34 at least partiallyoverlaps the second gear 68 of the second mixing paddle 36. This overlayautomatically retains the second mixing paddle 36 in the second sleeve32. The first gear 66 mates with the second gear 68 to rotate the secondmixing paddle 36 in the second rotational direction when the portion 28and the first mixing paddle 34 rotate in the first rotational direction,and vice versa. It is to be understood that the gear set 64 may bealternatively designed such that the first and second gears 66, 68 arenot required. As one non-limiting example, the gear set 64 could be abelt-drive system know to those skilled in the art.

Preferably, the mixing assembly 10 incorporates a gear ratio of thefirst gear 66 to the second gear 68 of 2:1. It is believed that thisgear ratio provides optimum mixing of the bone cement by the first andsecond mixing paddles 34, 36. However, it is to be understood that othergear ratios can be incorporated into the mixing assembly 10 withoutvarying the scope of the subject invention. It is also preferred thatthe first gear 66 and the second gear 68 are defined as spur gears.However, other gears known to those generally skilled in the mechanicalarts may be utilized within the context of the subject invention.

It is to be understood by those skilled in the art that the gear set 64may include additional gears beyond the first gear 66 and the secondgear 68. For example, the gear set 64 may further include a third gear65. If such an embodiment is desired, the first and second mixingpaddles 34, 36 could rotate in the same rotational direction at the sametime. Preferably then, the gear ratio would be established such that thefirst and second mixing paddles 34, 36 would rotate in the samerotational direction but about their respective fixed axes A1, A2 atdifferent rotational speeds. The third gear 65 and the portion 28 of thehandle 26 and the first and second mixing paddles 34, 36 all rotating inthe same direction at the same time are represented in FIG. 39.

In preferred embodiments of the subject invention, the handle 26 isoperatively coupled to the first mixing paddle 34 through the portion 28of the handle 26 that extends into the mixing chamber 22. However, it isto be understood that, as particularly disclosed in FIGS. 13 and 14, thehandle 26 can be operatively coupled to the second mixing paddle 36instead of the first mixing paddle 34. In such an embodiment, it isapparent to those skilled in the art that the gear set 64 would requiremanipulation to accommodate the interaction between the handle 26 andthe second mixing paddle 36.

In a further embodiment of the subject invention, the lid 14, which isremovably attachable to the housing 12, is movable between an openposition and a sealed position. The open position is particularlydisclosed in FIG. 40, and the sealed position is particularly disclosedin FIG. 41. In the open position for the lid 14, the bone cement can beadded to the housing 12. It is to be understood that the lid 14 can alsobe set on top of the housing 12, such that the bone cement cannotactually be added into the mixing chamber 22, yet the lid 14 is still inthe open position. In other words, the lid 14 is not in the sealedposition until the lid 14 is locked to the housing 12 as describedadditionally below. In the sealed position for the lid 14, the lid 14 ishermetically sealed to the housing 12 to define the sealed mixingchamber 22 between the lid 14 and the interior wall 16 of the housing12. The terminology “hermetically” is merely intended to indicate thatthe sealed mixing chamber 22 is impervious to external influences, ofcourse with the exception of the vacuum. As described above, the bonecement is mixed in the sealed mixing chamber 22.

This particular embodiment of the subject invention only requires onemixing paddle 34. For descriptive purposes, the one mixing paddle 34will be referred to as the first mixing paddle 34. As in the embodimentdescribed above, the first mixing paddle 34 is operatively coupled tothe portion 28 of the handle 26 for rotating with the portion 28. Thefirst mixing paddle 34 is movable between an extended position when thelid 14 is in the open position and a retracted position where the mixingpaddle is adapted to scrape the bone cement from the interior wall 16when the lid 14 is in the sealed position.

The first resilient member 60 is disposed between the portion 28 of thehandle 26 and the first mixing paddle 34. Preferably, the firstresilient member 60 is a compression spring. However, it is to beunderstood that the first resilient member 60 may be other types ofbiasing devices including, but not limited to, torsion springs and leafsprings. Of course, if alternative first resilient members 60 areutilized, then persons skilled in the art understand that certainmodifications structural modifications between the portion 28 of thehandle 26 and the first mixing paddle 34 may be required.

As described above, the first resilient member 60 is disposed about thecentering post 54 and within the socket 56. The first resilient member60 normally-biases the first mixing paddle 34 into the extendedposition. Importantly, the first resilient member 60 biases the firstand second mixing paddles 34, 36 downward into the housing 12 whetherthe mixing assembly 10 is being utilized with, or without vacuum.

The first resilient member 60 also compresses to permit the first mixingpaddle 34 to retract into the retracted position. The first resilientmember 60 compresses in response to contact between the first mixingpaddle 34 and the interior wall 16 of the housing 12 as the lid 14 ismoved from the open position to the sealed position, i.e., as the lid 14is put on the housing 12. As such, the lid 14 can be hermetically sealedto the housing 12 in the sealed position, yet the first mixing paddle 34can still scrape the bone cement from the interior wall 16, specificallyfrom a bottom 70 of the housing 12, due to the normal biasing of thefirst resilient member 60.

Due to the first resilient member 60, there is no space or gap betweenthe first set of tabs 52 extending from the portion 28 of the handle 26and the annular flange 48 of the first mixing paddle 34 when the lid 14is in open position (refer to the relationship between the first set oftabs 52 and the annular flange 48 in FIG. 40). However, as the lid 14 isbeing moved, i.e., rotated, about the housing 12 from the open positioninto the sealed position, the first mixing paddle 34 contacts the bottom70 of the housing 12 thereby forcing the first mixing paddle 34 upwardagainst the normal bias of the first resilient member 60 causing thefirst resilient member 60 to compress. As a result, there is a minorspace or gap established between the first set of tabs 52 and theannular flange 48 (refer to the relationship between the first set oftabs 52 and the annular flange 48 in FIG. 41). The significance of thisbiasing and compression of the first resilient member 60 relative to thefirst mixing paddle 34 is that a complete hermetic seal can beestablished while the first mixing paddle 34 is still biased to contactthe bottom 70 of the housing 12 such that the first mixing paddle 34 canstill effectively scrape the bone cement. More specifically, it is thesecond end 42 of the first mixing paddle 34 that actually contacts thebottom 70 of the housing 12 as the lid 14 is put on the housing 12. Thissecond end 42 also contacts the depression 20 defined within the housing12.

The housing 12 further includes a rim 72. The lid 14 mates with the rim72 upon moving from the open, i.e., unlocked, position to the sealed,i.e., locked, position. The mating of the lid 14 and the rim 72hermetically seals the lid 14 to the housing 12. Preferably, acompression sealing member 74 is disposed between the lid 14 and the rim72. Furthermore, to adequately retain the lid 14 attached to or on thehousing 12, a plurality of tabs 76, referred to as a second set of tabs76, are disposed about the lid 14 and a plurality of locking ramps 78are disposed about the rim 72 of the housing 12. Upon movement of thelid 14 from the open position to the sealed position, the tabs 76 of thelid 14 engage the ramps 78 of the housing 12 to lock the lid 14 to thehousing 12. As disclosed in FIG. 43, the tabs 76 and the ramps 78include mating nubs 79 to enhance locking.

Referring now to FIGS. 1 through 3, in a further embodiment of themixing bowl assembly 100, the lid 116 includes a seal 118 for creating aseal between the lid 116 and the annular flange lip 110 of the housing104 and further includes a connection for securing the lid 116 to thehousing 104. In one embodiment, the connection comprises a plurality ofprojections 111 extending from the housing 104 that engage a pluralityof locking ramps 113 in the lid assembly 102, thereby securing the lidassembly 102 to the housing 104. The lid assembly 102 may be mated tothe housing 104 by any other suitable connection such as threads or snapfittings. The lid 116, which is a component of the lid assembly 102,further includes a first cylindrical sleeve 122 for mounting a rotatablehandle assembly 124 thereon. The first cylindrical sleeve 122 receivesthe rotatable handle assembly 124, to be described below. The lidassembly 102 further includes a vacuum port 126 for attaching a vacuumsource and creating a vacuum within the mixing bowl assembly 100.

As shown in FIGS. 1 through 6, the rotatable handle assembly 124includes a grasping end 128 and a locking end 130 and extends outwardlyfrom the lid 116. The grasping end 128 includes a knob 132 disposedthereon allowing a user to grasp the rotatable handle assembly 124 androtate the handle assembly 124 in either a clockwise rotationaldirection, a counterclockwise rotational direction, or both. The knob132 may have a tab connector or any other suitable mating connector,wherein the handle assembly 124 is adapted for receiving the knob 132.The locking end 130 includes a socket 134 adapted for receiving a firstend 148 of the first mixing paddle 114. The socket 134 includes aplurality of external grooves 136, each of which includes a gasket 138disposed therein for providing a seal between the locking end 130 of therotatable handle assembly 124 and the first cylindrical sleeve 122.Preferably the gaskets 138 are O-rings. The socket 134 further includesat least one recess 140 adapted to retain the first mixing paddle 114,described below, such that one full rotation of the handle assembly 124causes the first mixing paddle 114 to complete one full rotation.

Referring to FIGS. 2 through 4, the first mixing paddle 114 includes aplurality of concave vanes 142 disposed about a central rotating axis144 wherein the plurality of concave vanes 142 extend from the centralrotating axis 144 and one contacts a wall 146 of the housing 104 whilethe other is spaced from the wall 146. This permits the vanes 142 toboth scrape the cement from the wall 146 and to spread the cement. Thecentral rotating axis 144 includes the first end 148, which includes aslot 150 and at least one beveled tab 152 disposed thereon. The beveledtab 152 is located on a flexible arm 153 and adapted for mating with theat least one recess 140 in the socket 134 of the rotatable handleassembly 124 such that when the first end 148 of the central rotatingaxis 144 is inserted into the socket 134 of the handle assembly 124, thetab 152 snaps into the recess 140 thereby securing the first mixingpaddle 114 to the handle assembly 124. This allows the first mixingpaddle 114 to rotate in accordance with the rotation of the handleassembly 124 while the central rotating axis 144 remains in a fixedposition relative to the handle assembly 124. Preferably, the socket 134includes at least two recesses 140 and the first end 148 includes twobeveled tabs 152. In this embodiment and all embodiments described belowthe first mixing paddle 114 is releasably secured to the handle assembly124 or lid assembly 102, as described below. This permits a user toremove and replace the first mixing paddle 114 with another first mixingpaddle having a different paddle design or other shape change that maybe required by the particular cement being mixed.

As shown in FIGS. 2 and 3, the central axis 144 further includes a firstannular flange 154 disposed thereon for supporting a first gear 156. Thefirst annular flange 154 includes a plurality of tabs 158 disposedthereon for securing the first gear 156 to the first annular flange 154such that the first gear 156 rotates in accordance with the handleassembly 124. The central axis 144 further includes a second end 159juxtaposed between the plurality of concave vanes 142 and received intothe depression 112 in the housing 104 for maintaining the axis ofrotation of the first mixing paddle 114 in the fixed position and forstabilizing the paddle 114 during rotation.

Referring back to FIG. 2, the lid assembly 102 further includes a secondcylindrical sleeve 162 disposed therein, with the sleeve 162 adapted tomount a second mixing paddle 164 having a plurality of vanes 166 anddefining a second rotating axis 168. The second rotating axis 168occupies a fixed position different than the fixed position of thecentral rotating axis 144 of the first mixing paddle 114 such that theplurality of concave vanes 142 of the first mixing paddle 114 rotatebeneath and around the second mixing paddle 164. The second mixingpaddle 164 includes a first end 170 having a plurality of tabs 172thereon. The sleeve 162 includes a widened area 163 for receiving andsecuring the rotating tabs 172, thereby securing the second mixingpaddle 164. As described above for the first mixing paddle 114 in thisand all other embodiments this is a releasable connection so a user canremove and replace the mixing paddle as required. The second rotatingaxis 168 includes a second annular flange 174 disposed thereon forsupporting a second gear 176. The second annular flange 174 includes aplurality of tabs 178 disposed thereon for securing the second gear 176to the second mixing paddle 164. Moreover, the second gear 176 iscoupled with the first gear 156 such that when the handle assembly 124is rotated in a first direction, thereby causing the first mixing paddle114 to rotate in the first direction, the second mixing paddle 164rotates in a second direction opposite of the first direction and thesecond rotating axis 168 remains in its fixed position.

Referring to FIGS. 7 and 8, another embodiment of the bone cement mixingbowl assembly of the present invention is generally shown at 200.Similar to the embodiment discussed above, the mixing bowl assembly 200includes a housing 104 as described above and a lid assembly 202.

The lid assembly 202 includes a lid 216 as described above with regardto covering and sealing the housing 104 and as shown in FIG. 4, arotatable handle assembly 124 as described above and shown in FIGS. 1through 4. The lid assembly 202 includes a first mixing paddle 214having a plurality of concave vanes 242 disposed about a centralrotating axis 244 wherein the plurality of concave vanes 242 extend fromthe central rotating axis 244 and contact a wall 246 of the housing 204.The central rotating axis 244 includes a first end 148 which includes aslot 250 and at least one beveled tab 252 disposed thereon. The beveledtab 252 is located on a flexible arm 253 and is adapted for mating withthe recess 140 in the socket 134 of the rotatable handle assembly 124such that when the first end 148 of the central rotating axis 244 isinserted into the socket 134 of the handle assembly 124, the tab 252snaps into the recess 140 thereby securing the first mixing paddle 214to the handle assembly 124. This allows the first mixing paddle 214 torotate in accordance with rotation of the handle assembly 124 while thecentral rotating axis 244 remains in a fixed position relative to thehandle assembly 124. Preferably, the socket 134 includes at least tworecesses 140 and first end 148 includes two beveled tabs 252.

Referring to FIG. 8, the central axis 244 further includes a beveledannular flange 254 having first 255 and second 257 layers disposedthereon for supporting a first gear 256. The first layer 255 of thebeveled annular flange 254 includes a plurality of tabs 258 disposedthereon for securing the first gear 256 to the beveled annular flange254 such that the first gear 256 rotates in accordance with the handleassembly 124. The central axis 244 further includes a second end 259juxtaposed between the plurality of concave vanes 242 and extendingtherefrom into a depression 212 in the housing 204 for maintaining theaxis of rotation of the first mixing paddle 214 and for stabilizing tothe paddle 214 during rotation.

As shown in FIGS. 7 and 8, the lid assembly 202 further includes aclosed-end sleeve 262 disposed therein, with the sleeve 262 adapted tomount a second mixing paddle 264 having a plurality of vanes 266 anddefining a second rotating axis 268. The axis 268 includes a pluralityof annular grooves 267, each of which has a gasket 269 to provide a sealbetween the second rotating axis 268 and the sleeve 262. Preferably, thegaskets 269 are O-rings. The second rotating axis 268 occupies a fixedposition different than the fixed position of the central axis 244 ofthe first mixing paddle 214 such that the plurality of concave vanes 242of the first mixing paddle 214 rotate around and beneath the secondmixing paddle 264. A first end 270 of axis 268 is adapted to be receivedinto the sleeve 262 such that when the first end 270 of the second axisof rotation 268 is inserted into the sleeve 262 the second mixing paddle264 rotates in a fixed position. The second rotating axis 268 includes asecond annular flange 274 disposed thereon for supporting a second gear276. The second annular flange 274 includes a plurality of tabs 278disposed thereon for securing the second gear 276 to the second mixingpaddle 264. Further, the second annular flange 274 is aligned with thefirst layer 255 of the beveled annular flange 254 and rests on thesecond layer 257 such that the second layer 257 rotates beneath thesecond annular flange 274 and provides increased support and stabilityto the second mixing paddle 264, which is important when the cement getsthick and rotation becomes more difficult. Moreover, the second gear 276engages with the first gear 256 such that when the handle assembly 224is rotated in a first direction, thereby causing the first mixing paddle214 to rotate in the first direction, the second mixing paddle 264rotates in a second opposite direction while the second rotating axis268 remains in its fixed position.

Referring to FIG. 9, a bone cement mixing bowl assembly according toanother embodiment of the present invention is generally shown at 300.The mixing bowl assembly 300 includes a lid assembly 302 along with thehousing 104, the rotatable handle assembly 124 and the first mixingpaddle 114 shown in the embodiment of FIGS. 1 through 6 as describedabove.

With reference to FIG. 9, the first mixing paddle 114 includes aplurality of concave vanes 342 disposed about a central rotating axis344 which is preferably integrally formed therewith, such as byinjection molding, wherein the plurality of concave vanes 342 extendfrom the central rotating axis 344 to contact a wall 346 of the housing104. The central rotating axis 344 is mated with the socket 134 in amanner similar to the embodiments shown in FIGS. 1 through 4 asdescribed above.

With further reference to FIG. 9, the central axis 344 is integrallyformed to have a first gear 356 thereon, such as through injectionmolding or any other suitable means, such that the first annular gear356 rotates in accordance with the handle assembly 124. The central axis344 further includes a second end 359 juxtaposed between the pluralityof concave vanes 342 and extending therefrom into the depression 112 inthe housing 104 for maintaining the central axis 344 of the first mixingpaddle 114 in the fixed position and stabilizing the paddle 114 duringrotation.

With continued reference to FIG. 9, the lid assembly 302 furtherincludes an attachment arm 362 disposed about the cylindrical sleeve 122and having an aperture 363 formed therein being adapted for mounting asecond mixing paddle 364 having a plurality of vanes 366 and defining asecond rotating axis 368. The second rotating axis 368 occupies a fixedposition different than the fixed position of the central axis 344 ofthe first mixing paddle 314 such that the plurality of concave vanes 342of the first mixing paddle 314 rotate around and beneath the secondmixing paddle 364. The second rotating axis 368 includes a first end 370having an annular groove 372 therein and having a split ring 373disposed in the groove 372 for retaining the second mixing paddle 364.The aperture 363 receives the first end 370 and secures the secondmixing paddle 364 therein. The second mixing paddle 364 is integrallyformed to include a second gear 376, such as through injection moldingor any other suitable means. Moreover, the second gear 376 engages thefirst gear 356 such that when the handle assembly 124 is rotated in afirst direction, thereby causing the first mixing paddle 314 to rotatein the first direction, the second mixing paddle 364 rotates in a secondopposite direction while the second rotating axis 368 remains in itsfixed position.

Referring to FIGS. 10 and 11, a bone cement mixing bowl assemblyaccording to another embodiment of the present invention is generallyshown at 400. The mixing bowl assembly 400 includes a lid assembly 402along with the housing 104, the rotatable handle assembly 124 and thefirst mixing paddle 114 shown in the embodiment of FIGS. 1 through 6 asdescribed above.

With further reference to FIG. 10, the first mixing paddle 114 includesa plurality of concave vanes 442 disposed about a central rotating axis444 wherein the plurality of concave vanes 442 extend from the centralrotating axis 444 to contact a wall 446 of the housing 104. The centralrotating axis 444 includes a first end 448 defining a shaft 450. Theshaft 450 is adapted for mating with an outer housing 435 which isfurther disposed in the socket 434 of the rotatable handle assembly 124such that when the first end 448 of the central rotating axis 444 isinserted into the socket 434 of the handle assembly 124, the shaft 450snaps into the outer housing 435 for securing the first mixing paddle114 to the handle assembly 124, thereby allowing the first mixing paddle114 to rotate in accordance with the handle assembly 124 while thecentral rotating axis 444 remains in a fixed position.

With further reference to FIG. 10, the outer housing 435 furtherincludes a first gear 456 that is threaded onto a threaded portion 437thereof such that the first gear 456 rotates in accordance with thehandle assembly 124. The socket 434 is received in the sleeve 122 of lidassembly 402. The threaded portion 437 secures the first gear 456 toouter housing 435. The central axis 444 further includes a second end459 juxtaposed between the plurality of concave vanes 442 and extendingtherefrom into the depression 112 in the housing 104 for maintaining thecentral axis 444 of the first mixing paddle 114 in the fixed positionand providing stability to the paddle 114 during rotation.

As shown in FIG. 10, the lid assembly 402 further includes an attachmentarm 462 disposed about the cylindrical sleeve 122 and having a channel463 formed therein being adapted for mounting a second mixing paddle 464having a plurality of vanes 466 and defining a second rotating axis 468.The second rotating axis 468 occupies a fixed position different thanthe fixed position of the first mixing paddle 114 such that theplurality of concave vanes 442 of the first mixing paddle 114 rotatearound and beneath the second mixing paddle 464. The second rotatingaxis 468 includes a first end 470 having an annular groove 472 thereonand including a split ring 473 disposed thereon for retaining the secondmixing paddle 464. The channel 463 receives ring 473 and secures thesecond mixing paddle 464 therein. The first end 470 of the second mixingpaddle 464 further includes a threaded portion 475 integrally formedtherewith. The second mixing paddle 464 further includes a second gear476 that is threaded onto the threaded portion 475 of the first end 470.Moreover, the second gear 476 engages with the first gear 456 such thatwhen the handle assembly 124 is rotated in a first direction, therebycausing the first mixing paddle 114 to rotate in the first direction,the second mixing paddle 464 rotates in a second opposite directionwhile the second rotating axis 468 remains in its fixed position.

As is clear to those skilled in the art, the handle assembly 124 and thesocket 134 may be disposed on the second mixing paddle 264 rather thanthe first mixing paddle 214. In FIG. 13, a bone cement mixing bowlassembly 500 according to this other embodiment of the present inventionis shown.

The mixing bowl assembly 500 is the same as the embodiment shown inFIGS. 7 and 8, except that the handle assembly 124 and the socket 134are disposed on a second mixing paddle 564 rather than a first mixingpaddle 514. The reference numbers have been retained as in FIGS. 7 and 8for ease of comparison. As would be understood by one of ordinary skillin the art, the same structures are shown in FIG. 13 as FIGS. 7 and 8,the only difference being which axis the structure is placed on. Themeans of rotatably securing the first mixing paddle 514 and the secondmixing paddle 564 to each other, to a lid assembly 502 and to thehousing 104 may be in accordance with any of the embodiments shown inFIGS. 1–12 and discussed herein or any other suitable means.

An alternative embodiment of the bone cement mixing bowl assembly 600 isshown in FIGS. 14–20. In this embodiment, the mixing bowl assembly 600includes a lid assembly 602 and a housing 604 forming a concave interiorand having an open top. The housing 604 includes a base 606 forsupporting the housing 604 and a rim 608 for securing the lid assembly602 to the housing 604. The housing 604 further includes a depression610 formed therein for stabilizing a first mixing paddle 666, describedbelow. The housing 604 of the present invention may be formed in avariety of suitable shapes as discussed above.

The mixing bowl assembly 600 further includes a rotatable handleassembly 616 and a vacuum port 618. The vacuum port 618 may furtherinclude a charcoal plug, not shown. As shown in FIGS. 15–17, the lidassembly 602 further includes a plurality of tabs 620 each of whichincludes a central notch 622. Alternately, the plurality of tabs 620 caninclude a nub instead of a central notch 622. The rim 608 includes acorresponding plurality of locking ramps 624. Each locking ramp 624includes a locking nub 626 and a ramp 628. The lid assembly 602 issecured to the housing 604 by placing the lid assembly 602 on the rim608 and rotating the lid assembly 602 relative to the housing 604 suchthat each locking nub 626 is received in a central notch 622 of itscorresponding tab 620 or each nub on the plurality of tabs passes overthe corresponding locking nub on the locking ramps. The rim 608 mayfurther include a sealing member, not shown, such as a strip of volara,as is known in the art. The lid assembly 602 includes a firstcylindrical sleeve 630 for mounting the rotatable handle assembly 616onto the lid assembly 602. The first cylindrical sleeve includes abeveled rim 634 that receives a seal 632 for sealing the connectionbetween the rotatable handle assembly 616 and the lid assembly 602, asshown in FIG. 14. The lid assembly 602 further includes a secondcylindrical sleeve 636 having an inward projecting rim 638.

As shown in FIGS. 18–20, the rotatable handle assembly 616 includes agrasping end 640 opposite a locking end 642. A knob 644 is receivedwithin a knob hole 648 located adjacent the grasping end 640. The knob644 includes a plurality of knob tabs 646 separated by cut-outs 650. Theknob 644 snaps into the knob hole 648. The locking end 642 of therotatable handle assembly 616 includes a socket 652 for receiving asecond mixing paddle 656, described below. The socket has a non-circularshape to enable transference of torque from rotation of the rotatablehandle assembly 616 to the second mixing paddle 656. The shape of socket652 can be square, hexagonal, or any other non-circular shape.

The second mixing paddle 656 includes a first end 654 having a shapeadapted to be received in the socket 652. In the embodiment shown thefirst end 654 includes a plurality of tabs 660 that are received in acorresponding number of recesses 658 in the rotatable handle assembly616, thereby positively locking the second mixing paddle 656 to therotatable handle assembly 616. The rotatable handle assembly furtherincludes a gear 664 for engaging a corresponding gear 676 on firstmixing paddle 666, described below. The second mixing paddle 656 furtherincludes a stop 662.

The first mixing paddle 666 comprises a central axis 670 and has aplurality of concave vanes 668, one of which touches a wall 672 of thehousing 604 and the other of which is spaced apart from the wall 672.Thus, as described above, one of the vanes 668 scrapes the bone cementoff the wall 672 while the other spreads the bone cement within thehousing 604. A first end 674 of the first mixing paddle 666 includes agear 676 that engages the gear 664 of the rotatable handle assembly 616.The first end 674 further includes a plurality of tabs 678 that arereceived in the second cylindrical sleeve 636 and snap in place byvirtue of the inward projecting rim 638, thereby securing the firstmixing paddle 666 to the lid assembly 602. A second end 680 of the firstmixing paddle 666 is received in the depression 610 thereby helping tomaintain the position of the central rotating axis 670. The secondmixing paddle 656 forms a second rotating axis 682. The lid assembly 602further includes a cut-out 614 enabling a user to place their hand onthe lid assembly 602 thereby steadying the assembly 600 while therotatable handle assembly 616 is rotated to mix a bone cement within thehousing 604. In this embodiment, as the rotatable handle assembly 616 isrotated the second mixing paddle 656 is rotated and the first mixingpaddle 666 is also rotated.

In FIG. 21, an alternative embodiment of the bone cement mixing bowlassembly is generally shown at 700. This assembly is similar to thatshown in FIGS. 14–20 with the exception that it includes at least athird mixing paddle 688. This third mixing paddle 688 is also disclosedin FIG. 42. The assembly 700 can include up to a total of four mixingpaddles like second mixing paddle 656 and third mixing paddle 688. Theonly difference between this embodiment and that shown in FIGS. 14–20 isthe addition of a third cylindrical sleeve 684 having an inwardprojecting rim 686. The third mixing paddle 688 includes a plurality ofsnap tabs 692 and a gear 690. The snap tabs 602 are received within thethird cylindrical sleeve 684 and engage the inward projecting rim 686 torotatably secure the third mixing paddle 688 to the lid assembly 602.The gear 690 engages the gear 676 of the first mixing paddle 666. Thus,rotation of the rotatable handle assembly 616 drives the first mixingpaddle 666, the second mixing paddle 656, and the third mixing paddle688. Addition of other mixing paddles would be accomplished by addingadditional cylindrical sleeves with inward projecting rims to the lidassembly 602. Although not shown, assembly 700 could also be designedsuch that vanes 668 are shorter, and mixing paddles 656, 688 are widersuch that the mixing paddles 656 and 688 scrape against wall 672.

The present invention has been described in an illustrative manner.Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is to be understoodthat the terminology that has been used is intended to be in the natureof words of description rather than of limitation.

1. A mixing assembly for mixing bone cement, said mixing assemblycomprising: a housing having at least one interior wall; a lid removablyattachable to said housing and movable between an open position wherethe bone cement can be added to said housing and a sealed position wheresaid lid is hermetically sealed to said housing to define a sealedmixing chamber between said lid and said interior wall of said housingfor mixing the bone cement; a handle having a portion extending throughsaid lid and being rotatable about said lid for mixing the bone cement;a mixing paddle operatively coupled to said portion of said handle forrotating with said portion wherein said mixing paddle is movable betweenan extended position when said lid is in said open position and aretracted position where said mixing paddle is adapted to scrape thebone cement from said interior wall when said lid is in said sealedposition; and a resilient member disposed between said portion and saidmixing paddle, said resilient member normally-biasing said mixing paddleinto said extended position and said resilient member compressing inresponse to contact between said mixing paddle and said interior wall assaid lid is moved from said open position to said sealed positionthereby permitting said mixing paddle to retract into said retractedposition such that said lid can be hermetically sealed to said housingin said sealed position, yet said mixing paddle can still scrape thebone cement from said interior wall.
 2. A mixing assembly as set forthin claim 1 wherein said mixing paddle includes a first end and a secondend wherein said first end is adjacent said lid and is operativelycoupled to said portion of said handle and said second end is adjacentsaid housing opposite said first end.
 3. A mixing assembly as set forthin claim 2 further comprising an annular flange disposed about saidmixing paddle at said first end.
 4. A mixing assembly as set forth inclaim 3 further comprising at least one hole defined within said annularflange with said portion of said handle extending into said at least onehole to operatively couple said mixing paddle to said portion of saidhandle.
 5. A mixing assembly as set forth in claim 4 wherein said atleast one hole is further defined as first and second holes defined withsaid annular flange wherein said first hole is defined within saidannular flange 180° apart from said second hole.
 6. A mixing assembly asset forth in claim 5 wherein said portion of said handle includes afirst set of tabs extending away from said handle with one of said tabsextending into said first hole to engage said annular flange at saidfirst hole and the other of said tabs extending into said second hole toengage said annular flange at said second hole for operatively couplingsaid first mixing paddle to said portion of said handle.
 7. A mixingassembly as set forth in claim 2 further comprising a post extendingfrom said first end of said mixing paddle away from said second end. 8.A mixing assembly as set forth in claim 7 wherein said portion of saidhandle includes a socket extending away from said handle to receive saidpost of said mixing paddle for operatively coupling said mixing paddleto said portion of said handle.
 9. A mixing assembly as set forth inclaim 8 wherein said post of said mixing paddle and said socket of saidportion of said handle are rectangular.
 10. A mixing assembly as setforth in claim 8 wherein said portion of said handle further includes acentering post disposed within said socket.
 11. A mixing assembly as setforth in claim 10 wherein said resilient member is disposed about saidcentering post, within said socket, and between said portion of saidhandle and said first end of said mixing paddle.
 12. A mixing assemblyas set forth in claim 2 wherein said mixing paddle is rotatable about afixed axis of rotation.
 13. A mixing assembly as set forth in claim 12further comprising a depression defined within said housing and alignedwith said fixed axis of rotation for receiving said second end of saidmixing paddle for maintaining said fixed axis of rotation and forstabilizing said mixing paddle during rotation.
 14. A mixing assembly asset forth in claim 1 further comprising a sleeve defined within andextending entirely through said lid for supporting said portion of saidhandle.
 15. A mixing assembly as set forth in claim 14 wherein saidportion of said handle extends through said sleeve to extend throughsaid lid.
 16. A mixing assembly as set forth in claim 15 wherein saidmixing paddle includes a first end and a second end wherein said firstend is adjacent said lid and is operatively coupled to said portion ofsaid handle extending through said sleeve and said second end isadjacent said housing opposite said first end.
 17. A mixing assembly asset forth in claim 16 further comprising an annular flange disposedabout said mixing paddle at said first end.
 18. A mixing assembly as setforth in claim 17 further comprising at least one hole defined withinsaid annular flange with said portion of said handle extending into saidat least one hole to operatively couple said mixing paddle to saidportion of said handle.
 19. A mixing assembly as set forth in claim 18wherein said at least one hole is further defined as first and secondholes defined with said annular flange wherein said first hole isdefined within said annular flange 180° apart from said second hole. 20.A mixing assembly as set forth in claim 19 wherein said portion of saidhandle includes a first set of tabs extending away from said handle withone of said tabs engaging said first hole of said annular flange and theother of said tabs engaging said second hole of said annular flange foroperatively coupling said mixing paddle to said portion of said handle.21. A mixing assembly as set forth in claim 16 further comprising a postat said first end of said mixing paddle extending from said annularflange.
 22. A mixing assembly as set forth in claim 21 wherein saidportion of said handle includes a socket extending away from said handleto receive said post of said mixing paddle for operatively coupling saidmixing paddle to said portion of said handle.
 23. A mixing assembly asset forth in claim 22 wherein said post of said mixing paddle and saidsocket of said portion of said handle are rectangular.
 24. A mixingassembly as set forth in claim 22 wherein said portion of said handlefurther includes a centering post disposed within said socket.
 25. Amixing assembly as set forth in claim 24 wherein said resilient memberis disposed about said centering post, within said socket, and betweensaid portion of said handle and said first end of said mixing paddle.26. A mixing assembly as set forth in claim 1 wherein said housingincludes a base for providing additional support to said housing.
 27. Amixing assembly as set forth in claim 1 wherein said housing includes arim and said lid mates with said rim upon moving from said open positionto said sealed position to hermetically seal said lid to said housing.28. A mixing assembly as set forth in claim 27 further comprising acompression scaling member disposed between said lid and said rim.
 29. Amixing assembly as set forth in claim 27 further comprising a pluralityof tabs disposed about said lid and a plurality of locking rampsdisposed about said rim of said housing, wherein said tabs of said lidengage said ramps of said housing upon movement of said lid from saidopen position to said sealed position.
 30. A mixing assembly as setforth in claim 1 wherein said mixing paddle includes a plurality ofvanes for mixing the bone cement.
 31. A mixing assembly as set forth inclaim 30 wherein said vanes are concave.
 32. A mixing assembly as setforth in claim 30 wherein said plurality of vanes includes a first vaneand a second vane, with said first vane in contact with said interiorwall for scraping the bone cement and with said second vane spaced fromsaid interior wall for spreading the bone cement.
 33. A mixing assemblyas set forth in claim 1 wherein said resilient member is further definedas a compression spring.
 34. A mixing assembly as set forth in claim 1further comprising a vacuum port defined within said lid.
 35. A mixingassembly for mixing bone cement, said mixing assembly comprising: ahousing having at least one interior wall; a lid removably attachable tosaid housing; a handle having a portion extending through said lid andbeing rotatable in a first rotational direction; a first mixing paddleoperatively coupled to said portion of said handle for rotating withsaid portion in said first rotational direction; a second mixing paddleoperatively coupled to said first mixing paddle for rotating oppositesaid portion such that said second mixing paddle rotates in a secondrotational direction, opposite said first rotational direction, whensaid portion and said first mixing paddle rotate in said firstrotational direction; and a gear set disposed between said first andsecond mixing paddles for operatively coupling said second mixing paddleto said first mixing paddle such that said second mixing paddle rotatesopposite said portion in said second rotational direction when saidportion and said first mixing paddle rotate in said first rotationaldirection; wherein said gear set includes a first gear associated withsaid first mixing paddle and a second gear associated with said secondmixing paddle, with said first gear mating with said second gear torotate said second mixing paddle in said second rotational directionwhen said portion and said first mixing paddle rotate in said firstrotational direction; wherein a gear ratio of said first gear to saidsecond gear is 2:1.
 36. A mixing assembly for mixing bone cement, saidmixing assembly comprising: a housing having at least one interior wall;a lid removably attachable to said housing; a handle having a portionextending through said lid and being rotatable in a first rotationaldirection; a first mixing paddle operatively coupled to said portion ofsaid handle for rotating with said portion in said first rotationaldirection; a second mixing paddle operatively coupled to said firstmixing paddle for rotating opposite said portion such that said secondmixing paddle rotates in a second rotational direction, opposite saidfirst rotational direction, when said portion and said first mixingpaddle rotate in said first rotational direction; and a first sleevedefined within and extending entirely through said lid for supportingsaid portion of said handle.
 37. A mixing assembly as set forth in claim36 wherein said portion of said handle extends through said first sleeveto extend through said lid.
 38. A mixing assembly as set forth in claim37 wherein said first mixing paddle includes a first end and a secondend wherein said first end is adjacent said lid and is operativelycoupled to said portion of said handle extending through said firstsleeve and said second end is adjacent said housing opposite said firstend.
 39. A mixing assembly as set forth in claim 38 further comprisingan annular flange disposed about said first mixing paddle at said firstend.
 40. A mixing assembly as set forth in claim 39 further comprisingat least one hole defined within said annular flange with said portionof said handle extending into said at least one hole to operativelycouple said first mixing paddle to said portion of said handle.
 41. Amixing assembly as set forth in claim 40 wherein said at least one holeis further defined as first and second holes defined with said annularflange wherein said first hole is defined within said annular flange180° apart from said second hole.
 42. A mixing assembly as set forth inclaim 41 wherein said portion of said handle includes a first set oftabs extending away from said handle with one of said tabs extendinginto said first hole to engage said annular flange at said first holeand the other of said tabs extending into said second hole to engagesaid annular flange at said second hole for operatively coupling saidfirst mixing paddle to said portion of said handle.
 43. A mixingassembly as set forth in claim 39 further comprising a post at saidfirst end of said first mixing paddle extending from said annularflange.
 44. A mixing assembly as set forth in claim 43 wherein saidportion of said handle includes a socket extending away from said handleto receive said post of said first mixing paddle for operativelycoupling said first mixing paddle to said portion of said handle.
 45. Amixing assembly as set forth in claim 44 wherein said post of said firstmixing paddle and said socket of said portion of said handle arerectangular.
 46. A mixing assembly as set forth in claim 44 wherein saidportion of said handle further includes a centering post disposed withinsaid socket.
 47. A mixing assembly as set forth in claim 46 furthercomprising a first resilient member disposed about said centering post,within said socket, and between said portion of said handle and saidfirst end of said first mixing paddle for biasing said first mixingpaddle.
 48. A mixing assembly as set forth in claim 39 furthercomprising a second sleeve at least partially spaced from said firstsleeve and extending from said lid for supporting said second mixingpaddle.
 49. A mixing assembly as set forth in claim 48 wherein saidsecond mixing paddle includes a first end and a second end wherein saidfirst end of said second mixing paddle is adjacent said lid and isdisposed within said second sleeve and said second end of said secondmixing paddle is adjacent said housing opposite said first end of saidsecond mixing paddle.
 50. A mixing assembly as set forth in claim 49further comprising a gear set disposed between said first and secondmixing paddles for operatively coupling said second mixing paddle tosaid first mixing paddle such that said second mixing paddle rotatesopposite said portion in said second rotational direction when saidportion and said first mixing paddle rotate in said first rotationaldirection.
 51. A mixing assembly as set forth in claim 50 wherein saidgear set includes a first gear supported on said annular flange of saidfirst mixing paddle and a second gear disposed at said first end of saidsecond mixing paddle, with said first gear mating with said second gearto rotate said second mixing paddle in said second rotational directionwhen said portion and said first mixing paddle rotate in said firstrotational direction.
 52. A mixing assembly as set forth in claim 51wherein said second gear of said second mixing paddle is recessed intosaid second sleeve.
 53. A mixing assembly as set forth in claim 52wherein said annular flange of said first mixing paddle at leastpartially overlaps said second gear of said second mixing paddle toautomatically retain said second mixing paddle in said second sleeve.54. A mixing assembly as set forth in claim 48 further comprising asecond resilient member disposed within said second sleeve between saidlid and said first end of said second mixing paddle for biasing saidsecond mixing paddle.
 55. A mixing assembly for mixing bone cement, saidmixing assembly comprising: a housing having at least one interior wall;a lid removably attachable to said housing; a handle having a portionextending through said lid and being rotatable in a first rotationaldirection; a first mixing paddle operatively coupled to said portion ofsaid handle and having a first fixed axis of rotation, said first mixingpaddle rotating with said portion in said first rotational directionabout said first fixed axis of rotation; a second mixing paddle having asecond fixed axis of rotation that is different from said first fixedaxis of rotation of said first mixing paddle; and a gear set disposedbetween said first and second mixing paddles to operatively couple saidsecond mixing paddle to said first mixing paddle such that said secondmixing paddle rotates opposite said portion in a second rotationaldirection, opposite said first rotational direction, and about saidsecond fixed axis of rotation when said portion and said first mixingpaddle rotate in said first rotational direction; wherein said gear setincludes a first gear associated with said first mixing paddle and asecond gear associated with said second mixing paddle, with said firstgear mating with said second gear to rotate said second mixing paddle insaid second rotational direction when said portion and said first mixingpaddle rotate in said first rotational direction; wherein a gear ratioof said first gear to said second gear is 2:1.
 56. A mixing assembly formixing bone cement, said mixing assembly comprising: a housing having atleast one interior wall; a lid removably attachable to said housing; ahandle having a portion extending through said lid and being rotatablein a first rotational direction; a first mixing paddle operativelycoupled to said portion of said handle and having a first fixed axis ofrotation, said first mixing paddle rotating with said portion in saidfirst rotational direction about said first fixed axis of rotation; asecond mixing paddle having a second fixed axis of rotation that isdifferent from said first fixed axis of rotation of said first mixingpaddle; a gear set disposed between said first and second mixing paddlesto operatively couple said second mixing paddle to said first mixingpaddle such that said second mixing paddle rotates opposite said portionin a second rotational direction, opposite said first rotationaldirection, and about said second fixed axis of rotation when saidportion and said first mixing paddle rotate in said first rotationaldirection wherein said gear set includes a first gear associated withsaid first mixing paddle and a second gear associated with said secondmixing paddle, with said first gear mating with said second gear torotate said second mixing paddle in said second rotational directionwhen said portion and said first mixing paddle rotate in said firstrotational direction; and a first sleeve defined within and extendingentirely through said lid for supporting said portion of said handle.57. A mixing assembly as set forth in claim 56 wherein said portion ofsaid handle extends through said first sleeve to extend through saidlid.
 58. A mixing assembly as set forth in claim 57 wherein said firstmixing paddle includes a first end and a second end wherein said firstend is adjacent said lid and is operatively coupled to said portion ofsaid handle extending through said first sleeve and said second end isadjacent said housing opposite said first end.
 59. A mixing assembly asset forth in claim 58 further comprising an annular flange disposedabout said first mixing paddle at said first end.
 60. A mixing assemblyas set forth in claim 59 further comprising a second sleeve at leastpartially spaced from said first sleeve and extending from said lid forsupporting said second mixing paddle.
 61. A mixing assembly as set forthin claim 60 wherein said second mixing paddle includes a first end and asecond end wherein said first end of said second mixing paddle isadjacent said lid and is disposed within said second sleeve and saidsecond end of said second mixing paddle is adjacent said housingopposite said first end of said second mixing paddle.
 62. A mixingassembly as set forth in claim 61 wherein said first gear is supportedon said annular flange of said first mixing paddle and said second gearis disposed at said first end of said second mixing paddle.
 63. A mixingassembly as set forth in claim 62 wherein said second gear of saidsecond mixing paddle is recessed into said second sleeve.
 64. A mixingassembly as set forth in claim 63 wherein said annular flange of saidfirst mixing paddle at least partially overlaps said second gear of saidsecond mixing paddle to automatically retain said second mixing paddlein said second sleeve.